# Allison J35

The General Electric/Allison J35 was the United States Air Force's first axial-flow (straight-through airflow) compressor jet engine. Originally developed by General Electric (GE company designation TG-180) in parallel with the Whittle-based centrifugal-flow J33, the J35 was a fairly simple turbojet, consisting of an eleven-stage axial-flow compressor and a single-stage turbine. With the afterburner, which most models carried, it produced a thrust of 7,400 lbf (33 kN).
Like the J33, the design of the J35 originated at General Electric, but major production was by the Allison Engine Company.

## Design and development

While developing the T31 axial turboprop in 1943 General Electric realized that they had the resources to design an axial flow turbojet at the same time as their centrifugal-flow J33 engine. They recognized the axial would have more potential for the future and went ahead with the TG-180 engine. GE axial compressor designs were developed from the NACA 8-stage compressor.
The engine had its starter and accessories (fuel control, fuel pump, oil pumps, hydraulic pump, RPM generator) mounted in the center of the compressor inlet. This accessory layout, as used on centrifugal engines, restricted the area available for compressor inlet air. It was carried over to the J47 but revised (relocated to an external gearbox) on the J73 when a 50% increase in airflow was required. It also had an inlet debris guard which was common on early jet engines.
GE developed a variable afterburner for the engine, although electronic control linked with engine controls had to wait until the J47. Marrett describes one of the potential consequences of manual control of the engine and afterburner on a turbine engine: if the afterburner lit but the pilot failed to ensure the nozzle opened, the RPM governor could overfuel the engine until the turbine failed.

## Operational history

The General Electric J35 first flew in the Republic XP-84 Thunderjet in 1946. Late in 1947, complete responsibility for the development and production of the engine was transferred to the Allison Division of the General Motors Corporation and some J35s were also built by GM's Chevrolet division. More than 14,000 J35s had been built by the time production ended in 1955.
The J35 was used to power the Bell X-5 variable-sweep research aircraft and various prototypes such as the Douglas XB-43 Jetmaster, North American XB-45 Tornado, Convair XB-46, Boeing XB-47 Stratojet, Martin XB-48, and Northrop YB-49. It is probably best known, however, as the engine used in two of the leading fighters of the United States Air Force (USAF) in the 1950s: the Republic F-84 Thunderjet and the Northrop F-89 Scorpion.
A largely redesigned development, the J35-A-23, was later produced as the Allison J71, developing 10,900 lbf (48.49 kN) thrust.

## Variants

Data from: Aircraft Engines of the World 1953, Aircraft Engines of the World 1950

### J35-GE-2

    3,820 lbf (17.0 kN) thrust, prototypes built by General Electric.

### J35-GE-7

    3,745 lbf (16.66 kN) thrust, built by General Electric, powered the 2 Republic XP-84 Thunderjet prototypes

### J35-GE-15

    4,000 lbf (18 kN) thrust, built by General Electric, powered the sole Republic XP-84A Thunderjet

### J35-A-3

    4,000 lbf (18 kN) thrust

### J35-C-3

    3,820 lbf (17.0 kN) thrust, production by Chevrolet.

### J35-C-3

    4,000 lbf (18 kN) thrust, production by Chevrolet.

### J35-A-4

    Similar to -29, 4,000 lbf (18 kN) thrust

### J35-A-5

    4,000 lbf (18 kN) thrust

### J35-A-9

    4,000 lbf (18 kN) thrust

### J35-A-11

    Similar to -29, 6,000 lbf (27 kN) thrust

### J35-A-13

    5,200 lbf (23 kN) thrust

### J35-A-15

    Similar to -29, 4,000 lbf (18 kN) thrust, powered the 15 Republic YP-84 Thunderjets

### J35-A-15C

    4,000 lbf (18 kN) thrust

### J35-A-17

    Similar to -29, 4,900 lbf (22 kN) thrust

### J35-A-17A

    Similar to -29, 5,000 lbf (22 kN) thrust

### J35-A-17D

    5,000 lbf (22 kN) thrust

### J35-A-19

    Similar to -17, 5,000 lbf (22 kN) thrust

### J35-A-21

    Similar to -35, 5,600 lbf (25 kN) thrust, 7,400 lbf (33 kN) with afterburner

### J35-A-21A

    Similar to -35, 5,600 lbf (25 kN) thrust, 7,400 lbf (33 kN) with afterburner

### J35-A-23

    Similar to -29, 10,900 lbf (48 kN) thrust, original designation for the Allison J71

### J35-A-25

    Similar to -29, 5,000 lbf (22 kN) thrust

### J35-A-29

    5,560 lbf (24.7 kN) thrust

### J35-A-33

    Similar to -35, 5,600 lbf (25 kN) thrust, 7,400 lbf (33 kN) with afterburner, without anti-icing

### J35-A-33A

    Similar to -35, 5,600 lbf (25 kN) thrust, 7,400 lbf (33 kN) with afterburner, without anti-icing

### J35-A-35

    5,440 lbf (24.2 kN) thrust, 7,200 lbf (32 kN) with afterburner

### J35-A-41

    Similar to -35, 5,600 lbf (25 kN) thrust, 7,400 lbf (33 kN) with afterburner, with anti-icing

### Model 450

    company designation for J35 series engines.

### General Electric 7E-TG-180-XR-17A

    ca 1,740 hp (1,300 kW) gas power, gas generator for the Hughes XH-17.

## Applications

* Bell X-5
* Boeing XB-47 Stratojet
* Convair XB-46
* Douglas D-558-1 Skystreak
* Douglas XB-43 Jetmaster
* Fiat G.84 (proposal only)
* Hughes XH-17 (experimental helicopter)
* Martin XB-48
* North American FJ-1 Fury
* North American XB-45 Tornado
* North American XP-86 Sabre
* Northrop F-89 Scorpion
* Northrop YB-49
* Republic F-84 Thunderjet
* Vought F7U-3 Cutlass (interim test usage)

## Engines on display

* Allison J35 is on public display at Texas Air Museum - Stinson Chapter, San Antonio, Texas
* Allison J35 is on public display at San Jose State University, San Jose, California
* Allison J35 is on public display at Flyhistorisk Museum, Sola, Norway

## Specifications (J35-A-35)

Data from , Aircraft engines of the World 1957

#### General characteristics

* Type: Afterburning turbojet
* Length: 195.5 in (4,970 mm) including afterburner
* Diameter: 37 in (940 mm)
* Frontal area: 7.5 sq ft (0.70 m$^2$)
* Dry weight: 2,315 lb (1,050 kg) without afterburner; 2,930 lb (1,330 kg) including afterburner

#### Components

* Compressor: 11-stage axial compressor
* Combustors: eight tubular inter-connected combustion chambers
* Turbine: single-stage axial turbine
* Fuel type: aviation kerosene, JP-4, MIL-F-5624 or 100/130 octane gasoline
* Oil system: dry sump pressure system with spur gear pressure and scavenge pumps at 35 psi (240 kPa)

#### Performance

* Maximum thrust: (dry): 5,600 lbf (25 kN) for take-off at 8,000 rpm
* Maximum thrust (wet): 7,500 lbf (33 kN) for take-off at 8,000 rpm
* Overall pressure ratio: 5:1
* Air mass flow: 95 lb/s (2,600 kg/min) at take-off power
* Specific fuel consumption: 1.1 lb/(lbf⋅h) (31 g/(kN⋅s)) dry; 2 lb/(lbf⋅h) (57 g/(kN⋅s)) wet
* Thrust-to-weight ratio: 2.63
* Maximum operating altitude: 50,000 ft (15,000 m)
* Cost: US$ 46,000 each